Disintegrating and deflocculating device in inlet boxes or papermaking machines

ABSTRACT

Apparatus for disintegrating coagulated fibrous material comprising a chamber, a stirring means therein including a first and second group of parallel spaced stirring bars, a first rotatable shaft, means for mounting the first group of stirring bars for rotation in parallel relation to each other and in parallel relation about the axis of said first shaft, means for mounting the second group of stirring bars for rotation in parallel relation to each other and in parallel relation about the axis of said second shaft, and means for rotating said shafts in opposite directions.

p 5, 1972 H. N. sKbLDKws'r 3,594,312w

DISINTEGRATING AND DEFLOCCULATING DEVICE IN INLET BOXES OF PAPERMAKINGMACHINES Original Filed April 1'7, 1969 4 Sheets-Sheet 1 p 26, 1972 H.N. SKGLDKVIST 4,

DISINTEGRATING AND DEFLOCCULATING DEVICE IN INLET BOXES OF PAPERMAKINGMACHINES Original Filed April 17, 1969 4 ShGOtS-ShBGt 2 P 1972 H. N.SKOLDKVIST 3,594,312

DISINTEGRATING AND DEFLOCCULATING DEVICE IN INLET BOXES or PAPERMAKINGMACHINES Original Filed April 17, 1969 4 Sheets-Sheet 3 P- 25, 7 H. N;SKOLDKVIST 3,594,312

DISINTEGRATING AND DEFLOCCULATING DEVICE IN INLET BOXES OF PAPERMAKINGMACHINES Original Filed-April 17, 1969 4 Sheets-Sheet 4.

United States Patent ()1 3,694,312 Patented Sept. 26, 1972 Rice3,694,312 DISINTEGRATING AND DEFLOCCULATING DE- VICE IN INLET BOXES ORPAPERMAKING MACHINES Helge Natanael Skiildkvist, deceased, late ofRundviksverken, Sweden, by Amy Maria Skiildkvist, Storgatan 28A, Umea,Sweden, Hans Marten Skiildkvist, 910 02, Rundviksverken, Sweden, andBirgitta Helena Paget, Regngation 4, Uppsala, Sweden, sole heirsContinuation of application Ser. No. 817,300, Apr. 17, 1969. Thisapplication May 25, 1971, Ser. No. 146,841 Claims priority, applicationSweden, Apr. 25, 1968, 5,577/68 Int. Cl. D21f J/06 US. Cl. 162-342 7Claims ABSTRACT OF THE DISCLOSURE Apparatus for disintegratingcoagulated fibrous material comprising a chamber, a stirring meanstherein including a first and second group of parallel spaced stirringbars, a first rotatable shaft, means for mounting the first group ofstirring bars for rotation in parallel relation to each other and inparallel relation about the axis of said first shaft, a second rotatableshaft coaxial with said first shaft, means for mounting the second groupof stirring bars for rotation in parallel relation to each other and inparallel relation about the axis of said second shaft, and means forrotating said shafts in opposite directions.

This application is a continuation of U.S. patent application Ser. No.817,300, filed Apr. 17, 1969, now abandoned.

In the making of paper, cardboard and fiberboards one of the mostdiflicult problems is the one of preventing flocculation While thesuspension of fibers passes through the inlet box or of disintegrating,effectively, flocks already formed. Another difficulty is the one ofbalancing the differences in speed across the machine and of spreadingthe suspension of fibers on the wire into a flow of a uniform thickness.

In an inlet box of a conventional construction the tendency of thefibers to clog and flocculate is due substantially to the nature of theflow while the suspension is passing through the inlet box and to theconsistency of the suspension. In order to prevent flocculation, theflow must be turbulent and the turbulence must exceed a given criticalvalue. It is essential that the pattern of flow in the inlet box shouldbe such that flocculation is prevented or flocks, already formed, aredisintegrated. This can be done by designing the inlet box in such amanner that during the entire time of flow there is always a suflicientdegree of turbulent flow. The usual way, however, is to subject thesuspension to occasional strong turbulent shearing stresses, which arestrong enough to cause disintegration of the flocks of fibers, andinbetween to allow the flow to proceed more quietly with less or noturbulence. -It is essential, however, that the period during which theflow proceeds more quietly should not be so long as to allow the fibersto clog to form disturbing flocks. The final formation of the Web on thewire is decisively determined by the way in which the turbulent forcesare generated and by the possibility of subsequently transforming thesuspension into a uniform flow moving at a constant speed of dischargeacross the entire width of the machine.

A common way of obtaining the aforementioned turbulence within thesuspension is by using, in the inlet box, stirring members in the formof single-rotating hollow rolls, barbed rolls or rolls provided withlongitudinally extending tubes. Another known method is the one ofgenerating the turbulence by injecting a liquid at a high speedangularly to the main direction of flow. The aforementionedconstructions, however, involve the disadvantage of not always making itpossible to introduce shear stresses of a size sufficient to bring aboutan effective disintegration of the flocks formed without simultaneouslydisturbing the profile of speed across the Web. Moreover, the flow ofthe suspension of fibers through the inlet box has not been such,either, that a flow of a uniform thickness could be obtained. Thepresent invention relates to means for improving the method ofdisintegrating flocks formed and for keeping the suspension of fibersunder so strong hydrodynamic shearing stresses that practically noflocculation of fibers can occur during the flow of the fibers from theinlet to the outlet of the box. At the same time said disintegratingmeans operates in such a manner that there cannot occur any disturbingvariations in speed across the direction of the machine, includingresulting non-uniform distribution of the substance.

For achieving the aforesaid object, the inlet box according to theinvention is characterized by at least one stirring means comprising atleast two groups of axial bars located between the side walls of the boxand adapted to rotate about a common shaft counter each other, eachalong its own path of rotation. According to the invention it ispossible to determine the surfaces of the paths of the stirring means insuch a manner that by choosing, in a suitable way, the number ofrevolutions of each group of bars the stirring work can be adjusted to asuitable level. By choosing a suitable number of bars, by choosing theirspeeds and the radii of their paths, the suspension of fibers flowingthrough the double-rotation stirrer will not leave the stirrer with anydisturbing unidirectional outflow, as is the case in ordinarysingle-rotation stirrers. Usually, several stirring devices are appliedin the inlet box. The suspension of fibers, subsequent to having passedthrough the last stirring device, will flow onto the wire without anyflocculation taking place, forming a layer of uniform thickness, andwithout any disturbing variations in speed occuring. By arranging thepairs of stirrers, having opposite directions of rotation in each pair,close to each other in the inlet box, the suspension of fibers all thetime will flow from one stirring device to the other, the time forflocculation between the individual stirring devices hereby becoming soshort that flocculation does not occur. If, however, on some occasion amore or less unidirectional outflow from one or all of the stirringdevices should be desired, this can most easily be done with or withoutadjusting the effect of disintegration by changing the number ofrevolutions of the individual stirrers of the stirring devices inquestion, or also by allowing rotation of only one of the stirrers, alldepending on the desired degree of the unidirectional outflow.

In order to prevent re-flocculation during the formation of the wetsheet, and particularly in the case of thick fiber webs and, forexample, when the forming is carried out in accordance with thedisclosure of the co-pending United States patent application No.724,665, filed Mar. 26, 1968 in the name of Helge Natanael SkiSldkvist,now deceased, it is possible to do so by connecting to and before theinlet box according to the present invention, a means for the generationof impulses, said means comprising a rotating drum having a certainnumber of longitudinally extending apertures, which at intervals andunder pressure discharge the suspension of fibers through an adjustableopening into the inlet box proper and the stirring devices of thelatter.

The frequency and the amplitude are controlled by the number ofrevolutions of the drum and by the pressure in the zone of the drum aswell as by the adjusted opening to the stirrer zone.

The pulsations or shocks thus obtained will spread through the inlet boxand to the gap between the bottom and top wires, and thereby preventre-flocculation of the fibers prior to when the solid wet sheet beginsto form.

Particularly in the making of thick fiber webs, it is advantageous,according to the invention, to subject the suspension of fibers duringits passage through the inlet box to hydrodynamic forces of such astrength that existent flocks of fibers become distintegrated and remaindisintegrated all the way to the outlet of the inlet box, and to impartto the suspension of fibers such vibrations or such pulsations that theyspread to the forming zone.

These and other details and advantages, characterizing the invention,will be evident from an embodiment of the inlet box provided withstirring devices according to the invention shown by way of example inthe accompanying drawings.

FIG. 1 is a schematic longitudinal section through a paper formingmachine with an inlet box provided with means according to theinvention, FIG. 2 is an enlarged partial view of the inlet box, in whichare provided disintegrating and stirring devices according to theinvention and impulse producing means in the form of a rotating drumhaving valve openings, PI-G. 3 is a sideview of the disintegratingdevices according to FIG. 2, and FIG. 4 shows, diagrammatically, thedriving of the disintegrating devices and of the impulse-producing drum.

The inlet box 1 merges into a tapering forming section 2, through whichthe upper wire 3 and the lower wire 4 extend.

The fiber suspension is pumped in at the bottom of the inlet box andpasses through a number of valve openings 5 in a rotating drum 6, whichis mounted in an ante-chamber 1a and which admits, intermittently, thesuspension of fibers to a passage 7. At the outlet end of said passagethe fiow is controlled by means of a slide valve 811 in order to providefor an adjustable opening 8. Thus, the inlet of the inlet box proper isformed by the openings 5, the passage 7 and the adjustable opening 8,the periodically occurring opening and closing of said inlet causing thesuspension of fibers to flow through the inlet box in a pulsating andpossibly also vibrating manner.

In the inlet box there are provided three disintegrating or stirringdevices 9, 10, 11 in accordance with the invention. For reasons ofsimplicity only the lowermost stirring device 9 will be described.

As will appear from FIGS. 2 and 3, the stirring device comprises twogroups of axial bars. One of the groups comprises three outer bars 12,13, 14 which are at their ends supported by radial spokes 15, 16 securedto two hubs 17, 18. The hub 17 is secured to one end of a driven shaft19, which extends through the side wall 20 of the inlet box and which ismounted in a bearing 21. The hub 18 forms a bearing around a seconddriven shaft 22, said shaft extending through the other side wall 23 ofthe box and all the way to the hub 17, in which the end of the shaft ismounted.

The other group of bars comprises four inner bars 24, 25, 26, 27 which,in relation to the path of rotation 28 of the outer bars, are situatedon an inner path of rotation 29 and supported by a number of radialspokes 30 secured to the shaft 22.

Each of said two shafts is provided with a sprocket wheel 31, 32. Thedriving of the sprocket wheel 31 and its associated sprocket wheels iseffected by a chain 33 and a motor 34. The drum 6 is driven by a motor35. On the other side of the inlet box there is provided correspondingmeans for driving the sprocket wheel 32 and the associated sprocketwheels of the other devices and 11. The sprocket wheels 31, 32 aredriven in such a manner that the outer bars will rotate in a directionopposite to that of the inner bars, as indicated by arrows along thepaths 28 and 29 in FIG. 2.

Within the scope of invention the number of bars in each group may bevaried according to desire. Furthermore it is possible to provide aplurality of groups of bars, having different paths of rotation butbeing supported by one and the same shaft, whereby a number of groups ofbars is obtained, said groups rotating in a direction opposite to thatof a number of groups of bars supported by the other shaft.

As shown in FIG. 2, it is suitable to have three equal- 1y spaced barsalong the outer path of rotation and four equally spaced bars along theinner path of rotation.

What is claimed is:

1. Apparatus for preventing flocculation of a fibrous suspension and fordisintegrating coagulated fibrous material comprising a chamber, withsidewalls, through which the suspension is passed, a stirring meanstherein including a first group and a second group of parallel spacedstirring bars extending substantially transversely across said chamber,a first rotatable shaft, means for rigidly mounting said first group ofstirring bars for rotation in parallel relation to each other and inparallel relation about the axis of said first shaft, the bars of saidfirst group being equally spaced from the axis of said first shaft, asecond rotatable shaft coaxial with said first shaft, means for rigidlymounting said second group of stirring bars for rotation in parallelrelation to each other and in parallel relation about the axis of saidsecond shaft, the bars of said second group equally spaced from the axisof said second shaft at a greater distance from the axis of rotationthan the bars of said first group, and means for rotating said shafts inopposite directions.

2. Apparatus as claimed in claim 1 wherein the number. of bars in thefirst group exceeds the number of bars in the second group.

3. Apparatus as claimed in claim 1 wherein the bars of each group arespaced equally from each other along their paths of rotation.

4. Apparatus as claimed in claim 1 wherein said first rotatable shaftextends substantially transversely across said chamber, wherein saidmeans for rigidly mounting said second group of stirring bars compriseshub members disposed within said chamber and adjacent the side wallsthereof and rotatably mounted on said first shaft, and wherein one ofsaid hub members is rigidly mounted for rotation by said second shaft,means for rigidly mounting said second group of stirring bars on saidhub members.

5. A device as claimed in claim 1 and further comprising means forintermittently introducing the fibrous suspension into said chamber toprovide a pulsating flow of the fibrous suspension through said chamber.

6. A device as claimed in claim 5 wherein the means for intermittentintroduction of fibrous suspension includes valve means for alternatelyopening and closing communication with said chamber.

7. A device as claimed in claim 1 wherein said chamber is provided withat least two stirring means sub-' stantially parallel to each other andspaced from each other substantially in the direction of flow of thefibrous suspension through said chamber.

References Cited UNITED STATES PATENTS 2,876,082 3/1959 Morrison 259- X2,440,727 5/1948 Rosmait 162-342 2,764,917 10/1956 Niks 162342 X FOREIGNPATENTS 616,209 6/1935 Germany 162-342 S. LEON BASHORE, Primary*Examiner A. L. CORBIN, Assistant Examiner US. Cl. X.R.

l622l6, 261, 343; 259l05

